difference in 91 rs computers
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Joined: Jun 2005
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From: northeast, oklahoma
Car: 1991 camaro rs
Engine: 3.1
difference in 91 rs computers
I have the computers out of both of my 91 rs's.
one is a 3.1l the other is a 305 tbi. the v8 computer has 2 slots for plugs and the 3.1l has 3 slots for 3 plugs?? my v8 has the plug from the engine harness and a plug from under the dash but the 3.1l rs has 2 plugs coming from underneath the dash for the third slot. (sorry about the lingo) what is the 2nd plug for? i am putting the 305tbi into the 3.1l equipped rs. i am royally confused at this point. please help
one is a 3.1l the other is a 305 tbi. the v8 computer has 2 slots for plugs and the 3.1l has 3 slots for 3 plugs?? my v8 has the plug from the engine harness and a plug from under the dash but the 3.1l rs has 2 plugs coming from underneath the dash for the third slot. (sorry about the lingo) what is the 2nd plug for? i am putting the 305tbi into the 3.1l equipped rs. i am royally confused at this point. please help 
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From: Chasing Electrons
Car: check
Engine: check
Transmission: check
You will want to use the TBI computer with the TBI engine. Easiest would may also be to swap over the EFI harness. If you don't swap the harness it will need to be re-pinned. In doing so 1 of the three plugs will be eliminated.
The 3.1l ECM with the 3 plugs is for a port injection setup. Where the TBI ECM is for, well, a TBI setup.
RBob.
The 3.1l ECM with the 3 plugs is for a port injection setup. Where the TBI ECM is for, well, a TBI setup.
RBob.
Thread Starter
Member
Joined: Jun 2005
Posts: 182
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From: northeast, oklahoma
Car: 1991 camaro rs
Engine: 3.1
i have eliminated the port injection harness and was planning on using the tbi harness i just wasn't sure what the third plug coming from under the dash was for? so i will eliminate one of the plugs which one will i know to eliminate ? also could you tell me wha the other plug was for? just curious! thanks for the info
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From: Chasing Electrons
Car: check
Engine: check
Transmission: check
I'm a bit lost on this third plug from under the dash. However, I may have an idea of what it is for. The 3.1l ECM received the VSS signal directly. Buffered it and sent it out to the speedometer and cruise control.
The TBI ECM does not do this. For that ECM there is a separate '4-OUT BUFFER' box. This box buffers the VSS signal and then sends it out to the ECM, speedometer, and cruise control.
The third plug may have been the VSS signals.
RBob.
The TBI ECM does not do this. For that ECM there is a separate '4-OUT BUFFER' box. This box buffers the VSS signal and then sends it out to the ECM, speedometer, and cruise control.
The third plug may have been the VSS signals.
RBob.
Thread Starter
Member
Joined: Jun 2005
Posts: 182
Likes: 0
From: northeast, oklahoma
Car: 1991 camaro rs
Engine: 3.1
sorry! when i pulled the ecm from the 3.1l rs there was the harness plug coming from the engine sensors, then there were 2 plugs that are coming from under the dash the tbi rs only has 1 plug instead of the 2 that the port injection car has. ok, if i don't use the "second" plug will my speedometer, and cruise still work? i will get you the numbers off of both ecm's tonight for you this might clear up some of my confusion.by the way (as if you couldn't tell
) this is my first ecm controlled swap. thanks for all of the help though!!
) this is my first ecm controlled swap. thanks for all of the help though!! 
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